Communication system with mobile terminal accessible to mobile communication network and local network simultaneously

ABSTRACT

In a communication system using a mobile terminal capable of accessing both a mobile communication network and a local network simultaneously and a gateway provided between a fixed communication network and the local network, the mobile terminal transmits an inquiry message for inquiring information regarding a location on networks of a correspondent of packet communications, to the gateway through the local network, and receives a response message indicating the lookup processing result from the gateway through the local network. Then, the mobile terminal acquires an address to be used in the packet communications with the correspondent according to the response message, and assigns the address to a communication interface for the local network.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mobile communication system using amobile terminal device which is capable of accessing both a mobilecommunication network and a local network simultaneously and a gatewaydevice for relaying between a fixed communication network and a localnetwork.

2. Description of the Related Art

In conjunction with the rapid spread of cellular phones and theInternet, the Internet service using a cellular phone as a terminal hasbeen developed by the mobile communication service providers. This is aservice in which a module for processing a communication protocol calledTCP/IP used in the Internet is provided in the cellular phone so as toenable WWW service, e-mail delivery, static image and video image datatransfer, etc. This service has an advantage in that it becomes possibleto freely access not just information closed within the communicationservice provider but also various information available on the Internetthat is spreading worldwide, and for this reason the number of users ofthis service is increasing rapidly.

Now, the cellular phone Internet service that has an enormous number ofusers encounters a serious problem regarding how to assign addresses toterminals. Currently, the Internet faces with the problem of IP addressshortage in view of the ever increasing number of nodes (routers andterminals), and in the current IPv4, it has been customary to use anaddress system called private address that is closed within anorganization for accesses in an enterprise network and to use globaladdresses only for accesses to the external of the organization byutilizing the address conversion. Similarly, in the case of the cellularphone Internet service, it is currently customary to use the privateaddress within the cellular phone network by providing an addressconversion device (NAT: Network Address Translator) at a border betweenthe IP packet network of the cellular phone company and the globalInternet.

On the other hand, the next generation IP specification called IPv6 iscurrently under the development. The IPv6 can accommodate far more nodescompared with the IPv4 by expanding the IP address from a 32 bits widthas used in the IPv4 to a 128 bits width. Similarly, in the case of thecellular phone Internet service, it is possible to assign unique globaladdresses to all terminals by adopting the IPv6. In this way,communications using a seamless end-to-end connection that does notrequire a relay device such as NAT on the communication path can berealized by using a wide address space, and it is expected to beadvantageous in many aspects including the security and the quality ofservice (QoS). Also, the IPv6 has a function called addressautoconfiguration for automatically generating an address from a networkID managed by each router and a unique ID of the device, and this isexpected to make the management of hosts easier.

Also, recently, in conjunction with the advance of the wirelesstechnology, the techniques for locally connecting various types ofdevices by a wireless network have been developed. One such technique isthe wireless standard called Bluetooth which connects devices in shortdistances by using 2.4 GHz unlicensed radio band. In the Bluetooth,devices can carry out mutual data communications by forming an ad-hocnetwork called pico-net. The similar network specification also includesthe HomeRF which is intended for use in the home network.

Now, using the IPv6 with the above described features, it is possible toconsider a situation where a portable terminal is capable of both theInternet access via the cellular phone network and the Internet accessvia the ISP (Internet Service Provider) network from a home network or alocal network such as the Bluetooth or the like. In such a situation,when the portable terminal starts the Internet communications usingeither the cellular phone network or the local network+the ISP network,the setting of the portable terminal can be made according to commandsfrom a router device on the cellular phone network or a router device onthe ISP network. However, in the case where the portable terminalreceives a service from the cellular phone network side while it alsomoves into the local network and carries out communications through thelocal network, there is a need to determine which one of the Internetaccess via the cellular phone network and the Internet access via thelocal network+the ISP network should be selected, and how the settingfor it should be made, according to some policy.

BRIEF SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a mobilecommunication system in which each mobile terminal device is capable ofmaking reasonable judgement and setting regarding the necessary addresssetting, appropriate communication route selection, etc., in the case ofmoving into the local network while receiving the communication serviceon the mobile communication network.

According to one aspect of the present invention there is provided acommunication system, comprising: a mobile terminal device capable ofaccessing both a mobile communication network and a local networksimultaneously; and a gateway device provided between a fixedcommunication network and the local network; the mobile terminal devicehaving: an inquiry message transmission unit configured to transmit aninquiry message for inquiring information regarding a location onnetworks of a correspondent of packet communications to be carried out,through the local network; the gateway device having: a lookup unitconfigured to carry out a lookup processing to determine whether thelocation of the correspondent on networks is on the local network, orwithin same management domain on the fixed communication network as themobile terminal device and outside the local network, or outside thesame management domain on the fixed communication network, uponreceiving the inquiry message from the mobile terminal device throughthe local network; and a transmission unit configured to transmit aresult of the lookup processing obtained by the lookup unit as aresponse message to the mobile terminal device through the localnetwork; and the mobile terminal device also having: an addressassignment unit configured to receive the response message from thegateway device through the local network, acquire an address to be usedby the mobile terminal device in the packet communications with thecorrespondent according to the response message, and assign the addressto a communication interface for the local network.

According to another aspect of the present invention there is provided amobile terminal device capable of accessing both a mobile communicationnetwork and a local network simultaneously, the mobile terminal devicecomprising: a first communication interface provided with respect to themobile communication network; a second communication interface providedwith respect to the local network; a packet communication unitconfigured to carry out first packet communications through the firstcommunication interface and second packet communications through thesecond communication interface; an inquiry message transmission unitconfigured to transmit an inquiry message for inquiring informationregarding a location on networks of a correspondent of packetcommunications to be carried out, through the second communicationinterface; and an address assignment unit configured to receive aresponse message in response to the inquiry message through the secondcommunication interface, acquire an address to be used by the mobileterminal device in the packet communications with the correspondentaccording to the response message, and assign the address to the secondcommunication interface.

According to another aspect of the present invention there is provided agateway device provided between a fixed communication network and alocal network, for relaying communications of a mobile terminal devicecapable of accessing both a mobile communication network and the localnetwork simultaneously, the gateway device comprising: a firstcommunication interface provided with respect to the fixed communicationnetwork; a second communication interface provided with respect to thelocal network; a packet communication unit configured to carry out firstpacket communications through the first communication interface andsecond packet communications through the second communication interface;a lookup unit configured to carry out a lookup processing to determinewhether a location of a prescribed device or service on networks is onthe local network, or within same management domain on the fixedcommunication network as a mobile terminal device and outside the localnetwork, or outside the same management domain on the fixedcommunication network, upon receiving an inquiry message for inquiringinformation regarding the location of the prescribed device or serviceon networks from the mobile terminal device through the secondcommunication interface; and a transmission unit configured to transmita result of the lookup processing obtained by the lookup unit as aresponse message to the mobile terminal device through the secondcommunication interface.

According to another aspect of the present invention there is providedan address assignment method for a mobile terminal device capable ofaccessing both a mobile communication network and a local networksimultaneously, the method comprising: transmitting an inquiry messagefor inquiring information regarding a location on networks of acorrespondent of packet communications to be carried out, from themobile terminal device through the local network; and receiving aresponse message in response to the inquiry message through the localnetwork at the mobile terminal device; acquiring an address to be usedby the mobile terminal device in the packet communications with thecorrespondent according to the response message; and assigning theaddress to a communication interface for the local network at the mobileterminal device.

According to another aspect of the present invention there is provided alookup service method of a gateway device provided between a fixedcommunication network and a local network, for relaying communicationsof a mobile terminal device capable of accessing both a mobilecommunication network and the local network simultaneously, the methodcomprising: carrying out a lookup processing to determine whether alocation of a prescribed device or service on networks is on the localnetwork, or within same management domain on the fixed communicationnetwork as a mobile terminal device and outside the local network, oroutside the same management domain on the fixed communication network,upon receiving an inquiry message for inquiring information regardingthe location of the prescribed device or service on networks from themobile terminal device through the local network at the gateway device;and transmitting a result of the lookup processing as a response messageto the mobile terminal device through the local network from the gatewaydevice.

According to another aspect of the present invention there is provided acomputer program product for causing a computer of a mobile terminaldevice capable of accessing both a mobile communication network and alocal network simultaneously, to execute an address assignment, thecomputer program product comprising: first computer program codes forcausing the computer to transmit an inquiry message for inquiringinformation regarding a location on networks of a correspondent ofpacket communications to be carried out, from the mobile terminal devicethrough the local network; second computer program codes for causing thecomputer to receive a response message in response to the inquirymessage through the local network; third computer program codes forcausing the computer to acquire an address to be used by the mobileterminal device in the packet communications with the correspondentaccording to the response message; and fourth computer program codes forcausing the computer to assign the address to a communication interfacefor the local network at the mobile terminal device.

According to another aspect of the present invention there is provided acomputer program product for causing a computer of a gateway deviceprovided between a fixed communication network and a local network, forrelaying communications of a mobile terminal device capable of accessingboth a mobile communication network and the local networksimultaneously, to provide a lookup service, the computer programproduct comprising: first computer program codes for causing thecomputer to carry out a lookup processing to determine whether alocation of a prescribed device or service on networks is on the localnetwork, or within same management domain on the fixed communicationnetwork as the mobile terminal device and outside the local network, oroutside the same management domain on the fixed communication network,upon receiving an inquiry message for inquiring information regardingthe location of the prescribed device or service on networks from themobile terminal device through the local network; and second computerprogram codes for causing the computer to transmit a result of thelookup processing as a response message to the mobile terminal devicethrough the local network.

Other features and advantages of the present invention will becomeapparent from the following description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an exemplary configuration of acommunication system according to one embodiment of the presentinvention.

FIG. 2 is a block diagram showing an exemplary configuration of agateway device in the communication system of FIG. 1.

FIG. 3 is a block diagram showing an exemplary configuration of a mobileterminal device in the communication system of FIG. 1.

FIG. 4 is a flow chart showing an exemplary processing procedure for oneoperation by the mobile terminal device of FIG. 3.

FIG. 5 is a block diagram showing a part of the communication system ofFIG. 1 for explaining one exemplary operation that can be carried out.

FIG. 6 is a block diagram showing a part of the communication system ofFIG. 1 for explaining another exemplary operation that can be carriedout.

FIG. 7 is a flow chart showing an exemplary processing procedure foranother operation by the mobile terminal device of FIG. 3.

FIG. 8 is a flow chart showing an exemplary processing procedure foranother operation by the mobile terminal device of FIG. 3.

FIG. 9 is a flow chart showing an exemplary processing procedure foranother operation by the mobile terminal device of FIG. 3.

FIG. 10A is a diagram showing an exemplary packet header to be used in amethod for switching a belonging network according to Mobile IPv6.

FIG. 10B is a schematic diagram for explaining a method for switching abelonging network according to Mobile IPv6.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1 to FIGS. 10A and 10B, one embodiment of a mobilecommunication system according to the present invention will bedescribed in detail.

FIG. 1 shows an exemplary configuration of a communication systemaccording to this embodiment.

In FIG. 1, a region enclosed by a dashed line 12 corresponds to a mobilecarrier network portion, while a region enclosed by a chain line 11corresponds to a home network portion.

In the following, the exemplary case where a mobile terminal device 20moves into the home network 11 while carrying out communications throughthe mobile carrier network 12 will be mainly described.

In the mobile carrier network 12, a plurality of network links areconnected through a cellular phone network 6 and router devices 4. Eachrouter device 4 has at least functions of an ordinary router compatiblewith the IPv6.

The mobile carrier network 12 is assumed to be originally providing theordinary voice communication service, but a configuration for providingthe ordinary voice communication service is omitted in FIG. 1. Note thatthis embodiment is directed to the exemplary case where one mobilecarrier manages its own packet communication network as a singlemanagement domain, but there can also be cases where one mobile carrierhas a plurality of management domains, cases where a plurality of mobilecarriers have a single common management domain, and any combination ofthese cases.

The mobile terminal device 20 (such as a portable terminal or a cellularphone, for example) will be connected to the corresponding network linkthrough a wireless base station 5 corresponding to a geographic locationof the mobile terminal device 20. Then, the mobile terminal device 20becomes capable of carrying out packet communications according to theIPv6 with a node located within the same network link, a node within thesame management domain through the router device 4, or a node (such as aserver 8, for example) located outside the management domain through therouter device 4 and the Internet 7.

On the other hand, in the home network 11, various types of devices 2and a gateway 1 are connected through a home local network 3. The mobileterminal device 20 has a function for accessing this home local network3.

Also, the gateway device 1 is assumed to be connected to the externalInternet 7 through a fixed communication network 9 (which is assumed tobe an ISP network here). Note that this embodiment is directed to theexemplary case where one Internet service provider manages its own rangefor providing the Internet connection service as a single managementdomain, but there can also be cases where one service provider has aplurality of management domains, cases where a plurality of serviceproviders have a single common management domain, and any combinationsof these cases.

The mobile terminal device 20 and the devices 2 connected to the homelocal network 3 are capable of carrying out packet communicationsaccording to the IPv6 with the server 8 on the Internet 7 through thegateway device 1 and the ISP network 9. In addition, they are alsocapable of carrying out packet communications according to the IPv6 witha server 10 for providing services limited only to members within theISP network 9, for example, when such a server 10 exists.

In this embodiment, the home local network 3 is assumed to be a localwireless network such as Bluetooth, for example.

Note that, in FIG. 1, the dashed line 12 and the chain line 11 aredepicted only for the sake of explaining the basic configurationlogically, and they do not indicate an area covered by the wirelessnetwork. In this embodiment mobile terminal device 20 is assumed to becapable of accessing both the mobile carrier network 12 and the homelocal network 3 simultaneously.

FIG. 2 shows an exemplary configuration of the gateway device 1 in thisembodiment.

As shown in FIG. 2, this gateway device 1 comprises a firstcommunication interface 31 for accessing the ISP network 9, a secondcommunication interface 32 for accessing the home local network 3, adata relay unit 33 for relaying between the first and secondcommunication interfaces 31 and 32, a service database 34, a servicelookup function unit 35, and a network monitoring unit 36. If necessary,the data relay device 33 may include a function for carrying out aprotocol conversion, a media conversion, etc., at a time of relayingbetween the first and second communication interfaces 31 and 32.

The service lookup function unit 35 is operated when a service lookupinquiry message is received through the the second communicationinterface 32, to look up the requested service through the servicedatabase 34 or inquire the requested service to another server andreturns the lookup result to the inquiring source.

The network monitoring unit 36 is operated when a network state inquirymessage is received through the second communication interface 32, toreturns a message containing information on a network state of the ISPnetwork 9 side to the inquiring source.

Note that the gateway device 1 may also have functions as the IPv6compatible router in the home local network 3, or another IPv6compatible router may be provided in the home local network 3.

FIG. 3 shows an exemplary configuration of the mobile terminal device 20in this embodiment.

As shown in FIG. 3, this mobile terminal device 20 comprises a firstcommunication interface 24 for accessing the mobile carrier network 12,a second communication interface 25 for accessing the home local network3, a voice communication unit 21 for carrying out ordinary voicecommunications, a packet communication unit 22 for carrying out packetcommunications according to the IPv6, an address register 23, anapplication list 26, and an active register 27.

The mobile terminal device 20 is capable of relating a plurality of IPv6addresses with respect to the same communication interface (capable ofsending packets by using a plurality of IPv6 addresses from the samecommunication interface). The address register 23 is used for thepurpose of storing these addresses.

A various IPv6 applications are to be operated on the mobile terminaldevice 20 side, and an application list 26 is used for storing a list ofthese applications (which includes information for identifying eachapplication (a file name, for example) and an application type of eachapplication, for example).

Also, when the specific application is activated by the user, the activeregister 27 registers information regarding the currently operatedapplication (such as information for identifying that application,application type of that application, and information for indicating acommunication interface used for that application (either the firstcommunication interface or the second communication interface), forexample).

Here, the address scope defined in the IPv6 will be described (see RFC2373 for further details).

In the IPv6, the following three address scopes are defined.

(1) Link Local Address

This is an address valid only within the same network link, which has aprefix of 1111 1110 10 in the IPv6.

(2) Site Local Address

This is an address valid only within the same management domain, whichhas a prefix of 1111 1110 11 in the IPv6.

(3) Global Address

This is an address which is unique over the entire Internet.

In the example of FIG. 1, the mobile terminal device 20 connected to themobile carrier network 12 can carry out communications using (arbitraryaddress containing) the link local address with respect to the server 4(which is in a positional relationship of being located) on the samenetwork link as the mobile terminal device 20, and communications usinga site local address (or a global address) with respect to a server(which is in a positional relationship of being located) in the samemanagement domain as the mobile terminal device 20. On the other hand,the mobile terminal device 20 connected to the mobile carrier network 12will carry out communications using a global address with respect to theserver 8 (which is in a positional relationship of being located) on thegeneral Internet 7.

Now, the first communication interface 24 of this mobile terminal device20 can be always assigned with one or both of the link local address andthe site local address. The link local address and the site localaddress will be derived from the prefix defined in the IPv6 and thedevice ID of this mobile terminal device 20. Note that it is alsopossible for the communication service provider to assign arbitraryaddress as an address to be used in the same network link. Also, whichone of the link local address alone, the site local address alone, andboth the link local address and the site local address is to be alwaysassigned can be determined according to the policy of the communicationservice provider.

By always assigning the link local address alone, the site local addressalone, or both the link local address and the site local address, themobile terminal device 20 becomes always capable of utilizing (carryingout communications for) on-link services using (arbitrary addresscontaining) the link local address (such as the advertisement deliveryfrom a specific wireless base station group, for example), and/orservices within domain which are services of the service provider inthis embodiment (such as information service limited to the users ofthat service provider, for example).

On the other hand, the global address to be assigned will be generatedfrom a network prefix delivered from the nearest neighbor router device4 and the ID information (EUI-64) of the mobile terminal device 20,according to the “Stateless Address Autoconfiguration” (RFC 2461)defined in the IPv6.

The basic procedure for the global address generation is as follows.Namely, the router device 4 regularly broadcasts a router advertisementmessage on-link, or the router device 4 returns a response message uponreceiving an inquiry message, and the mobile terminal device 20 receivesthe router advertisement message, or sends an inquiry message andreceives the response message, generates the global address by using thenetwork prefix contained in the received message, and transmits anaddress information notification message containing the generated IPv6address and a MAC address to the router device 4 side.

Upon receiving the address information notification message, the routerdevice 4 makes an entry of a corresponding information into acorresponding table called neighborhood cache (which corresponds to theARP table in the IPv4). As a result, the nearest neighbor router device4 will carry out the delivery of packets destined to the mobile terminaldevice 20.

Note that the user may be allowed to freely carry out the acquisition,setting and starting of the use of the IPv6 global address, or thediscarding, setting and ending of the use of the IPv6 global address.Alternatively, it is also possible to use a provision in which theprocessing for starting the use of the global address is carried outwhen the user of the mobile terminal device 20 activates an applicationthat requires the global address, and the processing for ending the useof that global address is carried out when that application is finished.

In this embodiment, the assignment of the global address to the secondcommunication interface 25 of the mobile terminal device 20 is to becontrolled using the above described address scope function.

In the example of FIG. 1, when the same network link is set to be withinthe home network 11, the mobile terminal device 20 connected to the homenetwork 11 can carry out communications using (arbitrary addresscontaining) the link local address with respect to a correspondent suchas the other device 2 or the gateway device 1 through the home localnetwork 3, and when the same site is set to be within the ISP network 9,the mobile terminal device 20 connected to the home network 11 can carryout communications using a site local address (or a global address) withrespect to a correspondent such as the server 10 within the ISP network9. On the other hand, the mobile terminal device 20 connected to the ISPnetwork 9 via the home network 11 will carry out communications using aglobal address with respect to the server 8 on the general Internet 7.

In the following, the operation in the case where the mobile terminaldevice 20 moves toward the home network 11 while receiving the serviceon the mobile carrier network 12 side by using the assigned globaladdress, and establishes a wireless link with the home local network 3to become a member of the home network 11, will be described.

FIG. 4 shows an exemplary processing procedure of the mobile terminaldevice 20 in this case.

First, the global address is assigned to the mobile terminal device 20at the mobile carrier network 12 side (step S11), and when the mobileterminal device 20 approaches to the home network 11 while receiving theservice on the mobile carrier network 12 side, the mobile terminaldevice 20 detects radio signals of the other devices and establishes alink (step S12). This wireless link establishing can be realized by amethod specified for each radio medium. At this point, if there is noparticular job that uses the local network on the Bluetooth side, itsuffices to wait in the wireless link established state.

Next, suppose that a service on the Bluetooth link side is requestedfrom the mobile terminal device 20. This request can be made by a taskunique to the mobile terminal device 20, or by sending a result of atask on the mobile carrier network 12 side to some device on theBluetooth network side by utilizing a direct bridging, for example.

At this point, the mobile terminal device 20 looks up a resource (adesired service) to be accessed on the Bluetooth side (step S13). Inthis case, it is possible to use various methods such as a method usingSDP (Service Discovery Protocol) defined in the Bluetooth, a methodusing SLP (Service Location Protocol) for looking up arbitrary serviceon the Internet, etc., and any suitable combination can be usedaccording to factors such as a range to be looked up, a type of aservice to be looked up, etc. Here, it is assumed that the resource onthe local Bluetooth link will be looked up by using the SDP first, andif it cannot be found, the wider range will be looked up by using theSLP. It is also possible to use a configuration in which the gatewaydevice 1 of FIG. 2 relays a query message for that purpose and becomesan agent of the SLP itself, for example.

Next, the mobile terminal device 20 acquires a necessary address (a linklocal address, a site local address or a global address) according to apositional relationship between the mobile terminal device 20 and thecorrespondent as obtained from the service lookup result, and assigns itto the second communication interface 25 (step S14). Then, the mobileterminal device 20 utilizes the desired service (step S15). Thereafter,the steps S13 to S15 will be repeated according to the need. However,the step S14 can be skipped when the necessary address is alreadyacquired.

Next, the above described service lookup result will be described forthree different cases.

First, in the case where the resource is found to be a link locallyaccessible one in the home local network 3 as a result of the servicelookup, the communications will be carried out by assigning the linklocal IPv6 address to the home local network 3 side in the mobileterminal device 20. This procedure will be used in the case of storingthe image data downloaded from the mobile carrier network 12 side into adisk for a PC as shown in FIG. 5, for example.

Next, in the case where the resource is found to be a site locallyaccessible one in the ISP network 9 on the home local network 3 side asa result of the service lookup, the communications will be carried outby assigning the site local IPv6 address to the home local network 3side in the mobile terminal device 20. This procedure will be used inthe case of receiving the service limited only to members of the ISPwhich is provided by the server 10 in the ISP network 9 as shown in FIG.6, for example.

On the other hand, in the case where the resource is found to be locatedon the global Internet 7 as a result of the service lookup, thecommunications will be carried out by assigning a global IPv6 address tothe home local network 3 side in the mobile terminal device 20. At thispoint, the mobile terminal device 20 becomes capable of accessing theresource located on the global Internet 7 either via the mobile carriernetwork 12, or via the gateway device 1 through the home local network3. This is the state called “multi-home” in which the mobile terminaldevice 20 becomes a router having two communication interfaces which areconnected to different providers.

In the case of this multi-home state, both of the communicationinterfaces can be made available. In such a case, one communicationinterface can be used mainly while the other communication interface isused as a back-up, and which communication interface should be usedmainly can be determined according to factors such as the congestionstate of each network, the charging state of each network, etc.

For example, the home network 11 side can be selected when the charge ismuch cheaper on the ISP network side (the fixed network side), or themobile carrier network 12 side can be selected when the network speed isfaster on the mobile carrier network 12 side. Also, the communicationinterface to be selected can be determined by accounting for adynamically varying state, instead of determining it fixedly. Such apolicy can be set by the user or a vendor of the terminal in advanceinto a control unit (not shown) inside the mobile terminal device 20.

Note that the state or the like of the ISP network 9 side may beacquired by inquiring it to the gateway device 1 or the like, forexample. Also, the mobile terminal device 20 itself may maintain thecharging condition or the like of the ISP network 9 side.

Similarly, the state or the like of the mobile carrier network 12 sidemay be acquired by inquiring it to a prescribed server device or thelike on the mobile carrier network 12 side, for example. Also, themobile terminal device 20 itself may maintain the charging condition orthe like of the mobile carrier network 12 side.

FIG. 7 shows an exemplary processing procedure of the mobile terminaldevice 20 in this case. Namely, in the case where the global address isavailable on both the mobile carrier network 12 side and the homenetwork 11 side (step S21 YES, step S22 YES), which one of the globaladdress on the mobile carrier network 12 side and the global address onthe home network 11 side should be used is determined according tovarious factors (step S23).

Now, while the processing on the home local network 3 side in the mobileterminal device 20 is carried out in this way, the job on the mobilecarrier network 12 side may be finished. This job status on the mobilecarrier network 12 side regarding the finished state can be detected byregularly checking the active register 27 in the mobile terminal device20. When all the jobs on the mobile carrier network 12 side arefinished, the entire network setting on the mobile carrier network 12side is released, such that the necessary setting is concentrated intothat on the home local network 3 side. This measure is taken from aviewpoint of not wasting the access channel resources unnecessarily.

FIG. 8 shows an exemplary processing procedure of the mobile terminaldevice 20 in this case. Namely, when all the jobs on the mobile carriernetwork 12 side are finished (step S31 YES), the entire network settingon the mobile carrier network 12 side is released (step S32).

Note that it is also possible to use a provision in which the mobileterminal device 20 transmits a message for notifying the finishing ofall the services received via the mobile carrier network 12 to thegateway device 1 through the home local network 3, and the gatewaydevice 1 notifies a message for setting up a global address (via the ISPnetwork 9) to be set up on the home local network 3 side to the mobileterminal device 20 upon receiving the above message from the mobileterminal device 20 if such a global address is not set up yet.

Now, it is also possible to use a provision in which the network settingon the mobile carrier network 12 side is not released but reserved as anemergency communication path for the device 2 on the home local network3 side to access the Internet 7 at a time of fault in the gateway device1 or the ISP network 9, for example. Even in this case, all the existingdevices 2 are initialized by the network setting on the home localnetwork 3 side, so that they cannot use the channel of the mobileterminal device 20 without a further change, and for this reason, thereis a need for the mobile terminal device 20 to function as a gatewaywith respect to the devices 2 on the home local network 3 side bycarrying out the NAT/Proxy processing, etc.

FIG. 9 shows an exemplary processing procedure of the mobile terminaldevice 20 in this case. Namely, when the mobile terminal device 20 isgoing to be a gateway of the home network side (step S41 YES), theNAT/Proxy processing, etc., are carried out (step S42).

Also, in practice, the mobile terminal device 20 establishes the networksetting on the home local network 3 side gradually, so that it ispossible to make a transition to the state of using a link on the homelocal network 3 side regardless of the communication interface on themobile carrier network 12 side.

Also, in the above, it is assumed that the communication interface to beused for the application is not to be changed during the communicationsfor that application, but it is also possible to change thecommunication interface at appropriate timing during the communicationsfor that application (from the mobile carrier network 12 side to thehome local network 3 side, for example).

Note that, for the job that requires the link local or site localresource access' on the mobile carrier network 12 side, thecommunication interface on the mobile carrier network 12 side is to beused until this job is finished (or until this job is cancelled).

Now, using the specification of the Mobile IPv6 which is currently underthe standardization process by the IETF, it is possible to guarantee themobility by regarding the mobile terminal device 20 that is actuallyconnected to the mobile carrier network 12 side as having moved to thehome local network 3 side. Here, a method for switching the belongingnetwork according to the Mobile IPv6 will be described with referencesto FIGS. 10A and 10B.

FIG. 10A shows an exemplary packet header in this case, which contains asource address (CN), a destination address (addr1) and a destinationoption (via addr2). Here, CN is a global address of the correspondent,addr1 is a global address of the mobile terminal device 20 on the mobilecarrier network 12 side, and addr2 is a global address of the mobileterminal device 20 on the home local network 3 side. Also, thedestination option specifies a location through which the packet shouldbe transferred.

Using the destination option of the IPv6, as shown in FIG. 10B, a packettransmitted from a correspondent 30 will be controlled to be transferredto the original address on the mobile carrier network 12 side via theaddress on the home local network 3 side. Then, in practice, the factthat this packet is destined to the mobile terminal device 20 isascertained when the packet is captured at the address on the mobilecarrier network 12 side, and the packet communication using a directroute becomes possible as the mobile terminal device 20 acquires thispacket.

In the above, the case where the mobile terminal device 20 moves fromthe mobile carrier network 12 side into the home local network 3 sidehas been described, but the reverse case where the mobile terminaldevice 20 moves from the home local network 3 side out to the mobilecarrier network 12 side can also be controlled similarly. Namely, themobile terminal device 20 can establish a wireless link with the mobilecarrier network 12 side, assign the necessary IPv6 addresses accordingto the address scopes of the necessary resources, and concentrates thesetting to that of the mobile carrier network 12 side by releasing theaddress setting on the home local network 3 side when the jobs on thehome local network 3 side are eventually finished. Also, the routeselection policy in the case of becoming the multi-home state in acourse of this operation can be determined similarly.

Also, in the above, it is assumed that the mobile terminal device 20 hasthe ordinary voice communication function, but the mobile terminaldevice 20 may have communication functions for information in otherforms such as text communications in addition to or instead of theordinary voice communication function. The mobile terminal device 20 maybe a device which is capable of utilizing only the Internet service. Thesimilar modifications are also possible with respect to the servicesprovided by the communication service provider.

As described, according to the present invention, in the case where themobile terminal device moves into the home local network while carryingout communications in the mobile carrier network, it is possible toconstruct the home local network side setting in the mobile terminaldevice phase by phase, according to the resources that become necessaryin the home local network.

Also, in the case where the mobile terminal device temporarily becomesthe so called multi-home state in which the IPv6 global addresses areassigned to both the home local network and the mobile carrier network,which one of the two communication interfaces should be used mainly canbe determined appropriately by accounting for the user's preferenceregarding the network state, the charging condition, etc.

In addition, in the case where the communication jobs on the mobilecarrier network side are finished, the mobile terminal device canrelease the network setting immediately such that all communications canbe concentrated to those via the home local network.

Furthermore, these setting conditions can be finely adjusted accordingto the user's preference, such that it is possible to freely devise apolicy (within a range of violating the scope rule for each application,for example) such as that all the jobs are re-constructed as the homelocal network based ones immediately once the wireless link with thehome local network is established, as long as no service dependent onthe mobile carrier network side is received, for example.

Thus according to the present invention, the mobile terminal device canjudge whether the resource necessary on the local network side is aresource that is on-link (a device with which communications can becarried out directly), or a resource that is closed within the samesite, or a resource other than these, by using the service lookup or thelike, and assign the IPv6 address of the scope corresponding to thatlocation to the local network side.

When the required resource is on the global Internet, it is accessiblefrom both the mobile communication network and the fixed network, and itis possible to judge whether the mobile terminal device is to become arouter in the multi-home state or the access is to be continued on themobile communication network side alone, for example, by accounting forthe network state, the charging condition, etc.

It is also possible to update the network setting such that the Internetservice can be continued by the fixed communication network side aloneby releasing the address on the mobile communication network side, whenall the services of the mobile communication network are finished as thetime elapses, for example. It is also possible to carry out the similarcontrol even in the case of making a transition from the fixedcommunication network to the mobile communication network in the reversedirection.

Consequently, according to the present invention, in the case where themobile terminal device moves into the local network while receiving thecommunication services on the mobile communication network side, it ispossible to determine the address setting, the communication routeselection, etc., on the local network side appropriately by accountingfor the user's policy, the necessary resources, etc.

Note that the home network used in the above described can be replacedby any other local network without affecting the applicability of thepresent invention.

Note also that, in the present invention, the existing IPv6 devices canbe used without requiring any modification, and the conventional IPv6addressing architecture can be used without any change. Consequently, itis advantageous in terms of the compatibility with the existing devices.

Note also that the present invention can be easily expanded according tothe network management policies of the various mobile carriers. Thepresent invention is also applicable not only to the IPv6 but also tothe packet communications using the cellular phones that are proposedrecently.

It is to be noted that the above described embodiments according to thepresent invention may be conveniently implemented using a conventionalgeneral purpose digital computer programmed according to the teachingsof the present specification, as will be apparent to those skilled inthe computer art. Appropriate software coding can readily be prepared byskilled programmers based on the teachings of the present disclosure, aswill be apparent to those skilled in the software art.

In particular, each of the gateway device and the mobile terminal deviceof the above described embodiment can be conveniently implemented in aform of a software package.

Such a software package can be a computer program product which employsa storage medium including stored computer code which is used to programa computer to perform the disclosed function and process of the presentinvention. The storage medium may include, but is not limited to, anytype of conventional floppy disks, optical disks, CD-ROMs,magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, magnetic or opticalcards, or any other suitable media for storing electronic instructions.

It is also to be noted that, besides those already mentioned above, manymodifications and variations of the above embodiments may be madewithout departing from the novel and advantageous features of thepresent invention. Accordingly, all such modifications and variationsare intended to be included within the scope of the appended claims.

1-3. (canceled)
 4. A mobile terminal device capable of accessing both amobile communication network and a local network simultaneously, themobile terminal device comprising: a first communication interfaceprovided with respect to the mobile communication network; a secondcommunication interface provided with respect to the local network; apacket communication unit configured to carry out first packetcommunications through the first communication interface and secondpacket communications through the second communication interface; aninquiry message transmission unit configured to transmit an inquirymessage for inquiring information regarding a location on networks of acorrespondent of packet communications to be carried out, through thesecond communication interface; and an address assignment unitconfigured to receive a response message in response to the inquirymessage through the second communication interface, acquire an addressto be used by the mobile terminal device in the packet communicationswith the correspondent according to the response message, and assign theaddress to the second communication interface.
 5. The mobile terminaldevice of claim 4, further comprising: a judgment unit configured tojudge a manner of utilizing the first packet communications and thesecond packet communications according to a prescribed policy, when boththe first packet communications and the second packet communications arepossible.
 6. The mobile terminal device of claim 5, wherein when theaddress assignment unit assigns one global address to the secondcommunication interface while the mobile terminal device is alreadyconnected to the mobile communication network by using another globaladdress through the first communication interface, the judgment unitjudges which one of the first packet communications using the anotherglobal address via the mobile communication network through the firstcommunication interface and the second packet communications using theone global address via the local network through the secondcommunication interface should be used, by accounting for at least oneof a state, a performance or a charging condition of the mobilecommunication network and a state, a performance or a charginginformation of an external communication network to which the localnetwork is connected.
 7. The mobile terminal device of claim 4, whereinthe address assignment unit assigns a link local address as defined inIPv6 to the second communication interface when the location of thecorrespondent is on-link, assigns a site local address as defined inIPv6 to the second communication interface when the location of thecorrespondent is within a site accessible from the second communicationinterface, or assigns a global address to the second communicationinterface otherwise.
 8. The mobile terminal device of claim 4, whereinthe packet communication unit releases an entire network setting on themobile communication network side or change a network setting of allapplications on the mobile terminal device to a network setting on thelocal network side, when all services received through the firstcommunication interface via the mobile communication network arefinished after accessing the local network through the secondcommunication interface.
 9. The mobile terminal device of claim 4,wherein the packet communication unit has a gateway function forrelaying packet communications of another device connected to the localnetwork by using the first communication interface and the secondcommunication interface, when both the first packet communicationsthrough the first communication interface and the second packetcommunications through the second communication interface are possible.10. The mobile terminal device of claim 4, wherein the secondcommunication interface supports Bluetooth as the local network.
 11. Themobile terminal device of claim 4, further comprising a voicecommunication unit configured to carry out voice communications. 12-16.(canceled)
 17. An address assignment method for a mobile terminal devicecapable of accessing both a mobile communication network and a localnetwork simultaneously, the method comprising: transmitting an inquirymessage for inquiring information regarding a location on networks of acorrespondent of packet communications to be carried out, from themobile terminal device through the local network; and receiving aresponse message in response to the inquiry message through the localnetwork at the mobile terminal device; acquiring an address to be usedby the mobile terminal device in the packet communications with thecorrespondent according to the response message; and assigning theaddress to a communication interface for the local network at the mobileterminal device.
 18. (canceled)
 19. A computer program product forcausing a computer of a mobile terminal device capable of accessing botha mobile communication network and a local network simultaneously, toexecute an address assignment, the computer program product comprising:first computer program codes for causing the computer to transmit aninquiry message for inquiring information regarding a location onnetworks of correspondent of packet communications to be carried out,from the mobile terminal device through the local network; secondcomputer program codes for causing the computer to receive a responsemessage in response to the inquiry message through the local network;third computer program codes for causing the computer to acquire anaddress to be used by the mobile terminal device in the packetcommunications with the correspondent according to the response message;and fourth computer program codes for causing the computer to assign theaddress to a communication interface for the local network at the mobileterminal device.
 20. (canceled)